Micro-Resolution Ultrasonic Imaging via Laser Vibrometry
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Solution Overview
Problem
Conventional ultrasonic imaging systems are limited in their ability to generate microscopic resolution images of internal features in materials due to large beam diameters and wavelength limitations, making it difficult to detect small defects and features like pores, cracks, and dis-bonded areas within materials.
Innovation Solution
A nondestructive testing system utilizing a focused immersion ultrasonic probe and a laser vibrometer to produce a tightly focused ultrasonic beam and a small laser beam, allowing for microscopic resolution imaging by aligning the laser vibrometer with the ultrasonic probe to detect ultrasonic vibrations through the material, reducing noise and scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasonic probes with large beam diameters are used, then the ultrasonic waves can propagate through the material, but the resolution for detecting small internal features deteriorates
Solution Approach 1:
The patent changes the frequency parameter of the ultrasonic wave to 100 MHz, which is significantly higher than conventional frequencies. This parameter change results in a proportionally smaller wavelength and beam diameter, enabling microscopic resolution imaging while maintaining effective propagation through the material.
Solution Approach 2:
The patent introduces a laser vibrometer to detect ultrasonic vibrations on the material surface, adding an optical detection dimension to the traditional acoustic transmission method. This enables resolution beyond the acoustic diffraction limit by detecting surface vibrations caused by transmitted ultrasonic waves.
2Reliability
If signal averaging methods are used to reduce noise, then the signal-to-noise ratio improves, but the scanning time increases significantly
Solution Approach 1:
The patent replaces the mechanical scanning and signal averaging process with a laser vibrometer that directly detects ultrasonic vibrations on the material surface. This substitution eliminates the need for repeated scans and signal averaging, achieving high signal-to-noise ratio without increasing scanning time.
Solution Approach 2:
The laser vibrometer detects ultrasonic vibrations directly on the material surface, allowing the system to obtain high-resolution information in a single pass without requiring external signal processing or repeated measurements to improve the signal-to-noise ratio.
3Measurement precision
If the ultrasonic beam is highly concentrated to increase interaction probability with small features, then the detection sensitivity improves, but the beam diameter becomes too small to cover sufficient area
Solution Approach 1:
The patent uses a laser vibrometer to detect ultrasonic vibrations on the material surface, adding an optical detection dimension that is not limited by acoustic diffraction. This allows the use of a highly concentrated ultrasonic beam for maximum interaction with small features while the laser detects vibrations over a broader area.
Solution Approach 2:
The laser vibrometer acts as an intermediary that converts ultrasonic vibrations into detectable optical signals. This intermediary enables the system to use a highly concentrated ultrasonic beam for maximum interaction probability while the laser detection provides broader coverage without being constrained by the small beam diameter.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves high-resolution C-scan images with improved signal-to-noise ratio, enabling the detection of microscopic features and distinguishing between bonded and un-bonded areas, as well as identifying defects like pores and fusion zones with increased accuracy and reduced scanning time.
Implementation Method 1
A tightly focused ultrasonic beam from the immersion ultrasonic probe and a laser beam from the laser vibrometer are both transmitted upon a sample
Implementation Method 2
The immersion ultrasonic probe comprises a focusing ultrasonic lens and piezoelectric transducer
Implementation Method 3
The beam size of a focused probe may be on the order of a few millimeters for the frequency range between 1 MHz and 10 MHz
Data Source
AI summary
A system and methods of nondestructive testing are described. The system includes an immersion ultrasonic probe and a laser vibrometer. The immersion ultrasonic probe and a sample are immersed in a fluid contained in an immersion tank and the laser vibrometer is disposed outside of the immersion tank. A tightly focused ultrasonic beam from the immersion ultrasonic probe and a laser beam from the laser vibrometer are both transmitted upon a sample, the laser beam being transmitted through the wall of the immersion tank. Since the ultrasonic beam is tightly focused and the laser beam samples only a small area impinged by the ultrasonic beam, microscopic resolution is obtained.